Indium arsenide gunn oscillator



INDIUM ARSENIDE GUNN OSCILLATOR Filed Oct. 19, 1966 OHMIC CONTACT INDIUMARSENIDE OHMIC CONTACT FIG. 1

22 20 24 )CONDUCTIVE BLOCK 28 26 PULSE SOURCE ARSENIDE UTILIZATION MEANSINVENTORS JOHN W. ALLEN MEGHA SHYAM BY GERALD L. PEARSON ATTORNEY$United States Patent ABSTRACT OF THE DISCLOSURE A Gunn type oscillatoris provided by applying pressure to a semi-conductor body, made ofindium arsenide for example, while applying an electric potentialthereacross.

This invention relates to microwave generators and, more particularly,to solid state devices for producing microwave oscillations.

It has been found that a crystal of a material such as Gallium Arsenidecan be made to emit microwaves by creases substantially following Ohmslaw, but when a threshold voltage is exceeded, the output of the crystalcomprises microwave oscillat'ons.

This phenomena is also being studied with other materials. One of thematerials being investigated is indium arsenide, since pseudo-potentialcalculations [M. L. Cohen cate that indium arsenide has a minimum at k=with a low effective mass and consequently a high mobility and lowdensity of states. Pseudo-potential calculations indi- E;, from valenceto conduction band 1s only 0.35 ev. at room temperature and since E; isless the impact ionizations.

An object of this invention is to enable indium arsenside to produceGunn oscillations in response to the application of a DC field.

Another object of the of a novel field of a material hold field forimpact ionization.

Still another object of the present invention is the provision of a newand useful microwave oscillator made of solid state material.

These and other objects of this invention are achieved by applying ohmiccontacts to the opposite large faces of a piece of tin-doped, n-typeindium arsenide. The ohmic contacts are applied to the faces which arein the 111) planes. Uniaxial pressure is applied to these opposite facesin a direction perpendicular thereto and parallel to curpulses areapplied across these opposite faces, and Gunn oscillations occur and maybe derived therefrom.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself both as to its organization and method of operation as well asadditional objects and advantages thereof, will best be understood fromthe following description when read in connection with the accompanyingdrawings, in which:

FIGURE 1 is an enlarged representation of an indium arsenide block whichmay be used in accordance with this invention as a Gunn oscillator, andi is a schematic representation of one manner of utilizing indiumarsenide in invention.

In accordance with uniaxial pressure can FIGURE 1 shows a block hasohmic contacts respectively 12, 14,

planes. By way of example, and not by way of a limitation of theinvention, a block such as shown in FIGURE 1, was cut from tin-dopedn-type material having dimensions 0.38 mm. x 0.38 mm. and 150,41. thick.The measured resistivity of these blocks was 10* ohm-cm. and the carrierdensity, 2.5 10 cmr corresponding to a mobility of 25,000 cm. /volt-sec.

Referring now to FIGURE 2, the indium arsenide block 0 was placed withina fixture of the type shown in FIG- A DC pulse source 26 was connectedby line 28 to the conductive blocks 16, 24, whereby DC pulses wereapplied across the indium arsenide block. Output from across the videdare at a frequency of 1.23:0.03 gc./s.

Succinctly stated, what occurs is believed to effect of the pressure isan applied electric field decrease the energy required to raiseelectrons in the be that the indium arsenide to their higher energylevel or 11l state.

There has been described and shown herein a novel, useful and uniquearrangement for altering the energy requirements in a semi-conductormaterial so that upon the application of an electric field, Gunnoscillations are caused to occur.

What is claimed is:

1. A Gunn oscillator comprising a semiconductor body, said semiconductorbody having the property that upon the application-of an electricalfield thereto, the threshold field required to produce impact ionizationis lower than that required to produce Gunn oscillations, means forapplying pressure to said semiconductor body to reduce the thresholdfield for Gunn oscillations below the threshold field for impactionization.

2. A Gunn oscillator as recited in claim 1 wherein said semiconductormaterial comprises indium arsenide.

3. A Gunn oscillator comprising a semiconductor body made of indiumarsenide, means for applying an electric potential across said indiumarsenide, and means for applying pressure to said indium arsenide toenable Gunn oscillations to occur in the presence of said potential.

4. The Gunn oscillator as recited in claim 3 wherein said means forapplying pressure to said indium arsenide applies a pressure whichexceeds 13 kilo'bars.

5. A Gunn oscillator as recited in claim 4 wherein said means forapplying an electric potential across said indium 4 arsenide bodyincludes a layer of indium on opposite faces of said indium arsenidebody.

6. A Gunn oscillator as recited in claim 3 wherein said means forapplying pressure applies said pressure to opposite faces of. saidindium arsenide which are in the (111) planes, and-said means forapplying a potential appliesthe potential to these planes.

References Cited A. R. Hutson et al.: Mechanism of the Gunn Effect Froma Pressure Experiment, Physical Review Letters, vol. 14, Apr. 19, 1965,pp. 639-641.

H. Kroemer: Theory of the Gunn Etfect," Proceedings of the IRE, December1964, 11.1736.

B. K. Ridley et al.: The Possibility of Negative Resistance Effects inSemiconductors, Proceedings of the Physical Society (London), vol. 78,August 1961, pp. 301-303.

R. Dobriner: Pace of Gunn-Effect Research Quickens, Electronic Design,Jan. 18, 1966, pp. 17, 18.

I. B. Gunn: Microwave Oscillations of Current in 111- V Semiconductors,Solid State Communications, vol. 1, pp. 88-91, 1963.

C. Hilsum: Transferred Electron Amplifiers and Oscillators, Proceedingsof the IRE, February 1962, pp. 189.

ROY LAKE, Primary Examiner. SIEGFRIED H. 'GRIMM, Assistant Examiner.

